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Please note that as of October 24, 2014, the Nokia Developer Wiki will no longer be accepting user contributions, including new entries, edits and comments, as we begin transitioning to our new home, in the Windows Phone Development Wiki. We plan to move over the majority of the existing entries. Thanks for all your past and future contributions.

Preference key must always be declared in config.xml file, in Series 40 Web Apps, prior to use. Failing to do so does not cause immediate error, but values stored are not preserved and lost when Web App is re-started.

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Preference key must always be declared in config.xml file, in Nokia Asha Web Apps, prior to use. Failing to do so does not cause immediate error, but values stored are not preserved and lost when Web App is re-started.

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Declaring preference in config.xml:

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Declaring preference in '''config.xml''':

<code xml>

<code xml>

<preference name="apikey"

<preference name="apikey"

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readonly="true"/>

readonly="true"/>

</code>

</code>

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<tt>readonly</tt> is an optional argument, thus can be omitted. If preference has read-only flag, scripts cannot change its value nor delete it.

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{{Icode|readonly}} is an optional argument, thus can be omitted. If preference has read-only flag, scripts cannot change its value nor delete it.

=== Accessing preferences ===

=== Accessing preferences ===

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Once preferences are declared you can use <tt>setItem()</tt> and <tt>getItem()</tt> or bracket access to modify stored values. Please note that in current Web tools (v 1.5), only bracket access is supported in local simulator preview. There is a size limit for stored preference. Stored string should not be longer than '''256 characters''', same applies for the key.

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Once preferences are declared you can use {{Icode|setItem()}} and {{Icode|getItem()}} or bracket access to modify stored values. Please note that in current Web tools (v 1.5), only bracket access is supported in local simulator preview. There is a size limit for stored preference. Stored string should not be longer than '''256 characters''', same applies for the key.

<code javascript>

<code javascript>

Line 56:

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</code>

</code>

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If you don’t need to use local simulator preview, setItem() and getItem() can be used to access stored preferences, as defined in Storage interface [http://www.w3.org/TR/webstorage/#storage-0]. Please note that <tt>NO_MODIFICATION_ALLOWED_ERR</tt> exception is not thrown in series 40 Web Apps, when trying to modify <tt>readonly</tt> preference.

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If you don’t need to use local simulator preview, {{Icode|setItem()}} and {{Icode|getItem()}} can be used to access stored preferences, as defined in Storage interface [http://www.w3.org/TR/webstorage/#storage-0]. Please note that {{Icode|NO_MODIFICATION_ALLOWED_ERR}} exception is not thrown in series 40 Web Apps, when trying to modify {{Icode|readonly}} preference.

<code javascript>

<code javascript>

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//get value, returns “null” if there is no match for the key

//get value, returns “null” if there is no match for the key

widget.preferences.getItem("key");

widget.preferences.getItem("key");

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</code>

</code>

=== Advanced usage ===

=== Advanced usage ===

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Among setItem and getItem, Storage interface offers following methods and attributes.

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Among setItem and getItem, Storage interface offers following methods and attributes.

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* <tt>length</tt>

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* {{Icode|length}}

** Total number of key/value pairs

** Total number of key/value pairs

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* <tt>key(n)</tt>

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* {{Icode|key(n)}}

** Returns name of the n:th key in the list

** Returns name of the n:th key in the list

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* <tt>removeItem("key")</tt>

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* {{Icode|removeItem("key")}}

**Removes key/value pair.

**Removes key/value pair.

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* <tt>clear()</tt>

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* {{Icode|clear()}}

**Removes all stored key/value pairs.

**Removes all stored key/value pairs.

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Note that in Series 40 Web Apps, <tt>removeItem(key)</tt> and <tt>clear()</tt> removes preferences event they would be defined as readonly.

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Note that in Nokia Asha Web Apps, {{Icode|removeItem(key)}} and {{Icode|clear()}} removes preferences event they would be defined as readonly.

<code javascript>

<code javascript>

Line 97:

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== Troubleshooting ==

== Troubleshooting ==

* Web App preferences are not stored correctly after deployment to device

* Web App preferences are not stored correctly after deployment to device

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** In some cases short URL deployment causes problems in Series 40 Web Apps version 1.5. Please use Bluetooth deployment when possible.

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** In some cases short URL deployment causes problems in Nokia Asha Web Apps version 1.5. Please use Bluetooth deployment when possible.

* Preferences are lost after reloading the web app

* Preferences are lost after reloading the web app

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** Make sure that you have declared preference in th <tt>config.xml</tt>

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** Make sure that you have declared preference in th {{Icode|config.xml}}

** Make sure that key and value are under 256 character limit.

** Make sure that key and value are under 256 character limit.

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*Preferences does not work in local simulator preview Series 40 Web Apps version 1.5

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*Preferences does not work in local simulator preview Nokia Asha Web Apps version 1.5

Contents

Widget preference allows developer to store data in key-value pairs. Series 40 Web App environment preserves stored data, and makes it available when Web App is started. Data stored into widget storage area is unique for Web App instance, i.e. preferences cannot be used to share data between two Web Apps.

Preference key must always be declared in config.xml file, in Nokia Asha Web Apps, prior to use. Failing to do so does not cause immediate error, but values stored are not preserved and lost when Web App is re-started.

Declaring preference in config.xml:

<preferencename="apikey"value="f1934gdf4tg334"readonly="true"/>

readonly is an optional argument, thus can be omitted. If preference has read-only flag, scripts cannot change its value nor delete it.

Once preferences are declared you can use setItem() and getItem() or bracket access to modify stored values. Please note that in current Web tools (v 1.5), only bracket access is supported in local simulator preview. There is a size limit for stored preference. Stored string should not be longer than 256 characters, same applies for the key.

//set value widget.preferences["key"]="value";

//get value, returns “undefined” if there is no match for the keyvar value = widget.preferences["key"];

If you don’t need to use local simulator preview, setItem() and getItem() can be used to access stored preferences, as defined in Storage interface [1]. Please note that NO_MODIFICATION_ALLOWED_ERR exception is not thrown in series 40 Web Apps, when trying to modify readonly preference.

//set valuewidget.preferences.setItem("key","value");

//get value, returns “null” if there is no match for the keywidget.preferences.getItem("key");